A Pakistani Christian man who was sentenced last year to life in prison for “blasphemy” was found dead Tuesday morning, according to officials in the Islamic republic.

Qamar David, who was charged with blasphemy in 2006 and imprisoned ever since, died of a heart attack sometime over the course of the night, officials told the press after David was found dead in his prison cell.

“There is no question about it; he died of natural causes," Sindh Inspector General of Prisons Ghulam Qadir Thebo told the BBC.

"Our investigations have not yielded any evidence of foul play," Thebo added after noting that David was assigned to the Christians-only wing of the prison.

"There is no evidence to suggest he was murdered."

Catholic new site AsiaNews, meanwhile, was informed by the police commissioner that David’s body was being held in the Civil Hospital in Karachi for an autopsy to confirm the cause of death.

Despite the insistence of Pakistani officials, David’s friends and family members are crying foul, noting that David was in “perfect condition” and that he had never complained of any illness, though he had been receiving threats against his life.

David, a businessman who resided in Karachi before his arrest, had been accused by a business rival of blasphemy – a crime punishable by death or life imprisonment.

On Feb. 25, 2010, a Karachi judge decided that David was guilty of uttering "outrageous" words against the Islamic prophet Muhammad and sentenced David to life in prison. David was convicted under Section 295-A of the blasphemy statues for “injuring religious feelings of any community,” and also under Section 295-C for derogatory remarks against Muhammad. In addition to the life sentence, David was also reportedly fined 100,000 rupees ($1,170).

Since his arrest, David had been reportedly threatened and beaten by the prison officials as well as other prisoners. His death follows the high-profile assassination of Minority Affairs Minister Shahbaz Bhatti, an outspoken critic of Pakistan's blasphemy laws and the only Christian in the Cabinet.

Christian leaders said Tuesday marked “another sad day for the minorities in Pakistan.”

"I am in grief. The whole Christian community has been grieving from past few days. We haven't recovered from the loss [of Bhatti] and this news has increased my concerns about the future of the Christians in Pakistan,” remarked the Catholic Bishop of Islamabad-Rawalpindi, Fr. Rufin Anthony.

“David was falsely accused of blasphemy,” the priest added, according to Spero News. “How much blood more do we still have to see to realize that the blasphemy laws need to be abolished? How much blood does the government wants to have on their hands?"

Under Pakistan’s blasphemy laws, violators can be sentenced to 10 years' imprisonment for insulting another's religious feelings; life imprisonment for defiling, damaging, or desecrating the Qur'an; and death for defiling Islam or its prophets.

Notably, however, some individuals have brought charges under these laws to settle personal scores or to intimidate vulnerable Muslims, sectarian opponents, and religious minorities. Furthermore, those accused of blasphemy and their families or religious communities are occasionally attacked and threatened with death by religious extremists – even after they are acquitted of blasphemy charges.

Presently, Islam is the state religion in Pakistan, and the constitution requires that laws be consistent with Islam. Muslims make up an estimated 97 percent of Pakistan's 180 million people.